Exercise therapy is prescribed for rehabilitating patients who have suffered certain types of physical injuries. Rehabilitative exercise for injured knee ligaments, for instance, is aimed at strengthening the muscles that flex or extend the leg. These are called, respectively, flexion and extension exercises. Flexion exercises work the hamstring muscles generally located in the posterior of the upper leg. On the other hand, extension exercises work the quadracep muscles generally located in the anterior of the upper leg. By exercising the affected knee and strengthening those muscles during rehabilitation, muscle atrophy in the injured limb is reduced or prevented altogether.
Exercising the injured knee during rehabilitation, especially after surgical repair of torn ligaments, preferably is performed under controlled conditions so as not to stress excessively the injured ligaments. Excessively stressing the injured ligaments can impede the healing process or even aggravate the injury.
Various commercially-available, general-purpose resistance machines are useful in providing controlled rehabilitative exercise. Among these is the CYBEX II isokinetic dynamometer made by the Cybex division of Lumex, Inc., N.Y., N.Y. In addition, U.S. Pat. No. 2,855,199 issued Oct. 7, 1958, and entitled EXERCISE DEVICE, and U.S. Pat. No. 3,465,592 issued Sept. 9, 1969, and entitled ISOKINETIC EXERCISE PROCESS AND APPARATUS, disclose other designs for such machines.
Generally, in known exercise machines of this type, the limb to be exercised is placed against a typically padded contact element that is drivingly connected to the resistance machine. Usually the extremity of the limb, e.g., the ankle, bears against the contact element. The contact element can take the form, for example, of an appliance that is removably worn by the patient during exercise.
For leg extension exercises, a seated patient wearing such an appliance bends his knee so as to swing his ankle upwardly against a resistance applied thereto through the appliance by the exercise machine. One form of exercise machine, known as an isokinetic dynamometer, enables isokinetic exercise throughout a high percentage of the full range of motion of the limb being exercised. Such machines can be manually set at a selected angular velocity (in degrees/second). The resistance machine then resists the force executed by the user so as to maintain the selected speed.
Various specially designed appliances have been suggested to control the application of force to an injured limb during rehabilitative exercise using such exercise machines. For instance, U.S. Pat. No. 4,407,496 discloses a variation for communicating the machine-generated force to two, spaced locations on the front of the leg being exercised, supposedly for counteracting detrimental shearing forces in the knee. The spaced, communicated forces are both applied in the same direction.
In accordance with that patent, the appliance has two, spaced-apart pads which are strapped on the front of the lower leg, an upper pad positioned just below the knee cap, and a lower pad positioned on the ankle. The pads are inter-connected by an elongate member of variable length. The inter-connecting member also pivotally connects to a resistance arm of the machine. The machine-generated force is communicated through the resistance arm to the appliance, through both pads thereof, and thence to the front of the leg. During extension exercise, the forces applied to the leg by the appliance both act in the same posterior direction to resist muscular force and, as mentioned above, supposedly, to counteract shear forces on the injured knee. The patented device is suggested for use during flexion as well as extension exercises.
Another therapeutic device is proposed in U.S. Pat. No. 4,502,681 to Blomqvist for use in rehabilitation of patients having degenerated tibia-femoral joints. That device supposedly reduces pressure between the femur and tibia during quadracep training by displacing the center of rotation of the resistance arm of the exercise machine anteriorly from the center of rotation of the knee. Consequently, the resistance arm and the patients leg follow two different arcs so as to slightly pull the tibia away from the femur.